Over the past thirty years flexible intermediate bulk containers, commonly known as bulk bags, have come into widespread use for receiving, storing, transporting, and discharging flowable materials of all types. Although circular bulk bags are known, bulk bags are typically constructed from rectangular panels which are sewn together along their adjacent edges to define a bulk bag which is initially square or rectangular in horizontal cross section. Nevertheless, all bulk bags, whether initially square, rectangular, or circular in cross section tend to assume a circular configuration when filled due to the uniform pressure imposed by the contents of the bulk bag against the flexible fabric side walls thereof.
U.S. Pat. No. 4,903,859 discloses a bulk bag comprising four double layer side walls. Stiffeners formed from cardboard are inserted between the layers of the side walls thereby imparting sufficient rigidity to the container to permit its use with liquids. Although the bulk bag of the '859 patent has been generally well received, its utilization has been somewhat limited by the fact that it cannot be stacked.
Co-pending application Ser. No. 09/390,403 assigned to the assignee hereof (doing business as Composite Container Corp.) discloses an improvement over the bulk bag of the '859 patent. In application Ser. No. 09/390,403 there is disclosed a bulk bag having double layer side walls and vertically extending corner pockets. Plywood sheets are received between the layers of the side walls and wooden posts are received in the corner pockets to provide a bulk bag suitable for use with liquids which is stackable.
U.S. Pat. No. 5,076,710 discloses a baffle-type bulk bag wherein bridge panels or baffles are sewn across the four corners of a nominally rectangular bulk bag. The baffles prevent the side walls of the bulk bags from bulging outwardly when the bulk bag is filled, thereby retaining the filled bulk bag in a more or less rectangular cross-sectional configuration. The baffles may be provided with apertures which allow material to flow into and out of the corners of the bulk bag during filling and discharging operations.
Co-pending application Ser. No. 09/458,362 also assigned to the assignee hereof discloses a baffle-type bulk bag which is stackable. In the bulk bag of application Ser. No. 09/458,362, triangular stiffeners are provided in the triangular corners of baffle-type bulk bags. The stiffeners may be formed from various materials including plastic panels, panels formed from corrugated paperboard and similar materials, etc. The stiffeners may be provided with apertures aligned with the apertures of the baffles thereby permitting the flow of material into and out of the bulk bag during filling and discharging operations.
The present invention comprises an improvement over the bulk bags disclosed in the '859 and '710 patents and in the '403 and '362 patent applications which provides an octagon shaped bulk bag which is stackable. The use of the octagon shape in the construction of the bulk bag is advantageous in that it provides maximum stackability while eliminating the need for baffles and triangular stiffeners contained within the baffles.
In accordance with the broader aspects of the invention, there is provided a bulk bag comprising eight double layer side wall portions. Each double layer side wall portion receives a stiffening panel which extends substantially the entire length and width of the side wall portion. The stiffening panels used in the side wall portions of the bulk bag of the present invention may comprise corrugated plastic panels or similar panels made from other materials which are sufficiently resistant to bending.
The octagon shaped bulk bags of the present invention are adapted for mounting on pallets. The bulk bag may also be provided with lift loops. The bulk bags of the present invention have bottom walls which may include a discharge port. Alternatively, one of the side wall panels may be provided with a discharge port located at the lower end thereof. The bulk bags of the present invention may have an open top, or a suitable top closure may be provided. Suitable top closures useful in the practice of the invention include openable flexible panels, openable rigid panels, and permanently mounted panels including fill spouts.
In accordance with another aspect of the invention, there is provided an eight piece bulk bag side wall construction. The eight pieces are arranged in four sets each comprising an inner layer and an outer layer. The inner and outer layers are joined together by vertically extending seams which are spaced apart by a distance equal to approximately 1/8 of the circumference of the bulk bag, thereby forming four of the side wall portions. The opposite edges of the inner and outer layers comprising the four side wall assemblies are joined edge to edge to form the remaining four side wall portions of the bulk bag. A stiffening panel is positioned between the inner and outer layers of each side wall portion and at least the bottom edges of the side wall sections are sewn together to secure the stiffening panels therein.